This invention relates to a vertical die casting machine or press of the general type disclosed in U.S. Pat. No. 5,429,175 which issued to the assignee of the present invention. In such a press, or a press as disclosed in U.S. Pat. No. 2,938,250, molten aluminum or metal is poured or injected into a shot sleeve above a shot piston which is connected to the piston rod of a vertical hydraulic shot cylinder. A mold is supported above the shot sleeve and defines one or more cavities which receive the molten metal from the shot sleeve when the shot piston is elevated by the hydraulic shot cylinder. The mold is formed in multiple sections and is held in a closed position by a vertical hydraulic clamping cylinder supported by the frame above the mold.
In order to obtain higher volume production, applicants' assignee has produced a vertical die casting press with two parallel spaced shot cylinders and corresponding shot sleeves and pistons which are shifted horizontally back and forth between a molten metal receiving or pour station and a metal transfer station where the molten metal is forced upwardly from each shot sleeve by its corresponding shot piston and shot cylinder into the mold cavity. With such an arrangement, one shot sleeve may be receiving molten metal at the pour station while simultaneously the molten metal is being pressed from the other shot sleeve into the mold cavity at the transfer station. However, the reciprocating movement or shuttle of the two vertical shot cylinders and the corresponding shot sleeves and pistons is relatively slow due to the mass of these components. As a result, it is difficult to obtain rapid transfer of the molten metal and high quality die cast parts without porosity. In addition, the movement of the hydraulic shot cylinders requires flexible hydraulic lines and significant maintenance.